Client and registration

Create a Fetcher for shared URL, headers, timeout, and interceptor policy. Requests still use the runtime's global fetch; a client does not own a connection pool or require destroy().

Construction and defaults

new Fetcher(options?: FetcherOptions) accepts the following options. Supplying an options object requires baseURL; omitting the object uses DEFAULT_OPTIONS.

Option	Default	Contract
baseURL: string	''	Used by the mutable urlBuilder; relative URLs still need a runtime that accepts them.
headers?: RequestHeaders	{'Content-Type': 'application/json'}	A supplied object replaces these constructor defaults. Each request gets a defensive, case-insensitive merge.
timeout?: number	undefined	Milliseconds; no timer until configured. Request 0 disables the inherited timeout.
urlTemplateStyle?	UrlTemplateStyle.UriTemplate	{id} syntax; Express selects :id.
interceptors?	New InterceptorManager	Supplied manager is used as-is; it can be shared across clients.
validateStatus?	200 <= status < 300	Used only when constructing the default manager.

urlBuilder, headers, and timeout can be changed for subsequent requests. interceptors is readonly as a property, while its registries remain mutable. Default header objects are shared references: replace client.headers or use request headers rather than mutating exported DEFAULT_OPTIONS.headers globally.

Choosing an entry point

Method	Input	Resolved value without an explicit extractor
resolveExchange(request, options?)	FetchRequest, RequestOptions	A synchronous FetchExchange; no HTTP I/O.
exchange(request, options?)	Same	Promise<FetchExchange> after the interceptor pipeline; does not extract a body.
request<R = FetchExchange>(request, options?)	Same	Promise<R> through the selected extractor; default exchange.
fetch<R = Response>(url, request = {}, options?)	FetchRequestInit	Promise<R>; default native Response.
get, head, options, trace	URL, request without method/body, options	Promise<R = Response>; method fixed by the helper.
post, put, patch, delete	URL, request without method, options	Same, with optional body.

DEFAULT_REQUEST_OPTIONS selects ResultExtractors.Exchange; DEFAULT_FETCH_OPTIONS selects ResultExtractors.Response. A generic such as get<User>() alone does not parse JSON: select an extractor or call response.json<User>(). Native Fetch may reject unsupported methods such as TRACE. See results and errors.

Named clients

new NamedFetcher(name, options?) extends Fetcher and immediately registers itself in the singleton fetcherRegistrar. fetcher is the exported default named instance, with DEFAULT_FETCHER_NAME = 'default'. Duplicate registration replaces the prior client.

FetcherRegistrar.register(name, client): void, unregister(name): boolean, and get(name): Fetcher | undefined manage entries. requiredGet(name) and the default getter throw Error when absent. Assigning default registers under 'default'; fetchers returns a new Map whose values are the same clients. Unregistering does not abort in-flight requests.

getFetcher(fetcher?, defaultFetcher?) accepts a direct instance, a registry name, or no value. An instance wins; a name must exist; a falsy argument chooses the supplied fallback and then the global default. FetcherCapable exposes that optional field. NamedCapable supplies name, and FetcherConfigurer.applyTo(fetcher): void is the structural contract used by configurable extensions.

Complete example

import {
  Fetcher,
  NamedFetcher,
  fetcherRegistrar,
  getFetcher,
} from '@ahoo-wang/fetcher';

const local = new Fetcher({
  baseURL: 'https://api.example.com',
  timeout: 3000,
});
const named = new NamedFetcher('reports', {
  baseURL: 'https://reports.example.com',
});
console.assert(getFetcher('reports') === named);
const exchange = local.resolveExchange({ url: '/users/1' });
console.assert(exchange.request.timeout === 3000);
fetcherRegistrar.unregister('reports');

Public symbols and source

Symbol	Implementation
FetcherOptions	fetcher.ts:52
DEFAULT_OPTIONS	fetcher.ts:87
RequestOptions	fetcher.ts:95
DEFAULT_REQUEST_OPTIONS	fetcher.ts:98
DEFAULT_FETCH_OPTIONS	fetcher.ts:101
Fetcher	fetcher.ts:124
FetcherCapable	fetcherCapable.ts:22
getFetcher	fetcherCapable.ts:37
DEFAULT_FETCHER_NAME	fetcherRegistrar.ts:19
FetcherRegistrar	fetcherRegistrar.ts:41
fetcherRegistrar	fetcherRegistrar.ts:166
NamedFetcher	namedFetcher.ts:38
fetcher	namedFetcher.ts:89
NamedCapable	types.ts:141
FetcherConfigurer	types.ts:248

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